"As part of this process, community involvement, including international, is essential for charting the new agency-wide strategy for our future Mars exploration efforts."

Scientists and technicians are being asked to submit ideas and abstracts online, wit the most promising to be presented during a workshop in June hosted by the Lunar and Planetary Institute in Houston.

"Receiving input from our community is vital to energize the planning process," says Doug McCuistion, director of the Mars Exploration Program.

"We'll integrate inputs to ensure the next steps for the Mars Exploration Program will support science, as well as longer-term human exploration and technology goals."

Several Mars missions are already in place. In August, the Mars Science Laboratory, Curiosity, will land on the planet's surface with the aim of discovering whether Mars has ever been able to support life - and whether there may be life present even now.

In 2013, NASA will launch the Mars Atmosphere and Volatile Evolution (MAVEN)orbiter, the first mission devoted to understanding the Martian upper atmosphere.